Cutting insert with cooling channel

ABSTRACT

A cutting insert for chipforming machine has a tip face with a cutting edge. Grooves are formed in the top face and extend toward the cutting edge. Chip-deflecting projections extend upwardly from the top face and are situated in spaces formed between adjacent grooves. A jet of cooling fluid is directed toward inner ends of the grooves and travels between the projections and within the grooves toward the cutting edge.

TECHNICAL FIELD OF THE INVENTION

This invention relates to a cutting insert intended for chip removingmachining, which is delimited by a top side, a bottom side and a numberof side surfaces extending therebetween, and which has at least onecutting edge between said top side and a side surface serving as aflank. Grooves which are mutually separated and open upwards, areprovided in said top side, in connection with the cutting edge, forfeeding cooling liquid in the direction towards the cutting edge.

GENERAL BACKGROUND OF THE INVENTION AND PRIOR ART

The practice of cooling not only the cutting inserts of cutting tools,e.g. tools for turning, but also the workpiece being machined by thetool as well as the chip being cut from the workpiece has been known fora long time. A fundamental aim within the technology of today forcutting machining is to enable the use of the highest possible pressurein the cooling liquid and to supply the liquid in the form of one ormore jets mainly directed towards the cutting insert and the chipreleased thereby. The higher the pressure that can be used in the liquidjet, the greater will be the possibility to use the liquid jet not onlyfor pure cooling, but also to obtain a mechanical effect on the chip,more precisely with the purpose of breaking up the chips into as smallparticles as possible. There are various opinions among those skilled inthe art about what, in this context, is to be considered as low and highliquid pressure, respectively. In general. though, the classificationwould be likely to be made in the following intervals:

low pressure <10 bar,

medium pressure 10-100 bar, and

high pressure>100 bar.

In older cutting tools, cooling was carried out using cooling liquid atlow-pressure, whereas somewhat more modem cutting tools have worked withcooling liquid at medium-pressure. In the more recent technology, theuse of liquid pressures of hundreds of bars is to be found. Forinstance, U.S. Pat. No. 5,148,728 forecasts the use of liquid pressuresas high as 2,800 bar.

When a cutting insert during, for instance, turning cuts loose a chipfrom a rotating workpiece, usually of metal, considerable amounts ofheat are generated. The actual cutting of the chip takes place in aprimary shear zone, which is developed in a peripheral portion of theworkpiece and extends obliquely upwards, from the cutting edge of thecutting insert. By virtue of the high temperatures developed, not onlyin the chip and the workpiece, but also in the cutting insert, the chipseparated in the primary shear zone cannot slide away across the topside of the cutting insert without being influenced by both friction andresistance. On the contrary, the very hot chip adheres to the topsurface of the cutting insert along a certain contact length during acourse of events, which has certain similarities to welding. The contactlength can, depending on e.g. the material of the workpiece, varybetween tenths of a millimetre to a few millimetres backwards from ashear zone which is near the cutting edge. In doing so, the hot materialis strongly adhered in a thin layer, above which the proper cutting ofthe chip takes place by shearing in a secondary shear zone (frequentlydesignated as the weld zone). Hereafter, a so-called friction zonefollows, along which the chip is in forceful frictional contact with thecutting insert before leaving this. In order to facilitate theseparation of the chip from the cutting insert, mostly some sort of chipdeflector is provided; e.g. in the form of bumps or projections on thetop side of the actual cutting insert and/or in the form of specificbodies on the tool, in particular clamps for the retention of thecutting insert.

The modern high-pressure cooling-liquid technology aims at introducingthe cooling-liquid jet into the substantially wedge-shaped spaceprovided between the bottom side of the chip and the top side of thecutting insert at the point where the chip is initially separated fromthe cutting insert. The idea is to form a so called hydraulic wedgebetween the chip and the top side of the cutting insert, and that saidwedge should contribute to “break out” the chip and, as far as possible,reduce the extent of the contact length of the chip along the cuttinginsert. A fundamental aim with the introduction of high-pressure coolingliquid between the chip and the cutting insert is, of course, also tocool these as effectively as possible. However, the attempts to improvethe cooling and the flow of the chip away from conventional cuttinginsert carried out hitherto have not been entirely successful.

OBJECTS AND FEATURES OF THE INVENTION

The present invention aims at obviating the above-mentioned shortcomingsof previously known technology and at providing a cutting insert havingimproved capabilities to more efficiently cool and remove the chips. Aprimary object of the invention is, therefore, to provide a cuttinginsert which permits access of high-pressure liquid jets to the areabelow the zone along which the chip is separated from the cuttinginsert, at the same time as the chip should be broken out from the topside of the cutting insert as effectively as possible. Another object isto provide a cutting insert that guarantees the intended improvement ofthe cooling and the removal of chips by means of simple and therebyinexpensive means, more precisely by providing the cutting insert with anew geometric shape.

According to the invention, at least the primary object is attained bythe providing a top face of an insert with grooves extending toward thecutting edge, and with upwardly extending chip-deflecting projections 9.At least a portion of each projection is disposed closer to the cuttingedge than is an inner end of an adjacent groove. A jet of cooling fluiddirected toward the inner ends of the grooves travels between theprojections and within the grooves toward the cutting edge.

Further Elucidation of Prior Art

A cutting insert specially constructed for forming threads is previouslyknown through DE 3 740 814, the said insert having a number of groovesfor feeding cooling liquid in the direction towards the cutting edge ofthe cutting insert in the top side thereof. More precisely, threecomparatively wide grooves are recessed in the top side of the cuttinginsert and arranged to co-operate with a separate clamp having thepurpose of holding the cutting insert in the appurtenant seat and, atthe same time, serving as a chip deflector. The grooves together withthe bottom side of the clamp, therefore, define ducts to which coolingliquid is fed from a central main duct in the frame of the cutting tool.This implies, among other things, that the cooling liquid may not be fedin the form of jets with high pressure. Furthermore, this way of feedingthe cooling liquid is limited to only the cutting inserts being held byclamps.

BRIEF DESCRIPTION OF THE APPENDED DRAWINGS

The drawings show:

FIG. 1 a perspective view of a first, simple embodiment of a cuttinginsert according to the invention,

FIG. 2 a planar view from above of the cutting insert according to FIG.1.

FIG. 3 a section A—A in FIG. 2,

FIG. 4 a planar view corresponding to FIG. 2 of a cutting insertaccording to a second, alternative embodiment of the cutting insert,

FIG. 5 a planar view showing a third embodiment of the cutting insertaccording to the invention,

FIG. 6 a section B—B in FIG. 5,

FIG. 7 a section C—C in FIG. 5,

FIG. 8 an enlarged, detailed view showing an individual groove incross-section,

FIG. 9 an enlarged, detailed section showing a cutting insert accordingto FIGS. 5-8 during the turning of a workpiece, and

FIG. 10 a planar view showing a fourth, alternative embodiment of thecutting inserts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

In FIGS. 1-3 a cutting insert 1 is shown, which is delimited by a topside 2, a bottom side 3 as well as a number of side surfaces 4 extendingtherebetween. In the example shown, the number of side surfaces is four.Thus, the insert is of polygonal shape as viewed in top plan. There is acutting edge 5 between the top side 2 and a side surface 4, which servesas a flank. At the corners of the cutting insert, the straight cuttingedge portion 5 transforms into a rounded cutting edge portion 5′. In thegenerally square-shaped cutting body, there is a central hole 6 for afixing screw (not shown), by means of which the cutting insert may befastened in a seat of a cutting tool, e.g. for turning. Parts of thistool are outlined at 7 in FIG. 9.

A number of mutually separated grooves 8, are provided in connectionwith the cutting edge 5 and said grooves open upwards in the top side ofthe cutting insert. Projections 9 are arranged between adjacent grooves8 in a manner which is characteristic for the invention, theseprojections protrude from the top side of the cutting insert andtogether form a chip deflector for each chip cut loose by the cuttingedge. As may be clearly seen in FIGS. 1 and 3, the individual groovesextend from an area close to the central hole 6, all the way to theflank 4. Thus, in the embodiment example according to FIGS. 1-3, eachindividual groove opens up into the flank 4.

An outer portion 9 a of each projection is disposed closer to thecutting edge 5 than is the inner end 8 a of an adjacent groove 8, and isalso disposed father from the cutting edge than is an outer end 8 b ofthe groove, as shown in FIGS. 2 and 5. The outer ends 8 b of the grooves8 intersect the top side 2 at a location 8 c which is at a lowerelevation than an uppermost portion 9 b of each projection, as can beseen in FIG. 3.

The embodiment according to FIG. 4 differs from the embodiment accordingto FIGS. 1-3 only in the fact that sets of grooves 8 are arranged alongeach one of the four side cutting edges or cutting edges of the cuttinginsert. In other words, the cutting insert according to FIG. 4constitutes an indexable insert.

Reference is now made to FIGS. 5-8, which illustrate a third,alternative embodiment of the cutting insert according to the invention.The only fundamental difference between this cutting insert and thecutting insert being visualised in FIGS. 1-3 is that the individualgrooves 8 end at a certain distance from the appurtenant cutting edge 5.Accordingly, in this case, the cutting edge 5 extends unbroken betweentwo corners of the cutting insert.

As may be clearly seen in FIGS. 7 and 8, the individual groove 8 has anupwardly diverging cross-sectional shape. More precisely, the groove isdelimited by two oblique side walls 10, 10′, which at the bottomtransform into a mutual bottom surface 11 having a rounded shape. Theindividual groove should have a depth that is larger than the widththereof on a level with the top surface of the cutting insert 2. Inpractice, on a level with the top surface, the groove can have a width Win the range of 0.2-0.4 mm, whilst the depth—calculated from the bottomsurface 11 to the level of the top surface 2—can be in the range of0.4-0.6 mm. In FIG. 7, numeral 12 designates a land between two adjacentgrooves 8. The width of this land portion should be at least twice aslarge as the width w of the individual groove 8 on a level with the landportion. In practice, therefore, the width of the land portion amountsto 0.8-1.2 mm or more.

The shape of the individual chip deflector projection 9 should begenerally rounded. Thus, as may be seen in FIG. 6, a convexly roundedcrown surface transforms into the top surface 2 and a land portion 12,respectively, via concavely rounded transition surfaces. Laterally, theindividual projection may advantageously be delimited by extensions ofthe cutting edge-shaped, diverging side surfaces 10, 10′, defining thegroove 8.

In FIG. 10, an indexable insert is shown with four sets of groovesinstead of only one set of grooves in accordance with FIG. 5.

It should be noted that the projections 9 in all types of embodimentsare placed entirely or partly outside the inner ends of the grooves 8,situated closest to the central hole 6. In the drawings, these innerends of the grooves are designated 13.

Function and Advantages of the Cutting Insert According to the Invention

How a rotating workpiece 14 is submitted to a turning operation by meansof the cutting insert I together with the appurtenant tool 7 isschematically shown in FIG. 9. In doing so, the cutting insert cuts achip designated by 15. The separation of this chip 15 from the workpiece14 is initiated in a primary shear zone, which is outlined in FIG. 9 bymeans of the dotted line 16. In a portion of the chip, designated by 17,there is a secondary shear zone, along which the chip finally isseparated. The material adheres to the top side of the cutting insert ina thin layer below this shear zone, and a friction zone then followsthis before the chip finally leaves the cutting insert.

The number 18 designates a cooling-liquid jet which is ejected at highpressure from a nozzle (not shown) included in the tool and directedagainst the area between the under side of the chip 15 and the top sideof the cutting insert. The pressure in the cooling liquid which leavesthe nozzle can to advantage be within the range of 250-1,000 bar, oreven more.

Thanks to the presence of the grooves 8 in combination with the chipguiding elements in the form of the projections 9 at least a portion ofwhich is situated between adjacent grooves, the cooling-liquid jet 18can be led into the space below the chip 15. More precisely, a feedingof the cooling liquid to the immediate vicinity of the cutting edgetakes place in the form of a number of partial flows in each of thegrooves 8. This implies that the jet operating with high pressure isgiven improved capability to affect the chip mechanically, inasmuch asthis in at least the friction zone is broken up at a steeper angle tothe top side of the cutting insert than with previously knowntechnology. This means that the contact length of the chip, from thecutting edge to the point when it separates from the cutting insert, maybe reduced. At the same time, the steeper the breaking angle of the chipthe easier it is to break it into smaller pieces. Another importantadvantage of the grooves is that the cooling of the chip as well as ofthe cutting insert is made more effective. In this way, the chip will becooled from below in an improved way by the partial flows of the coolingliquid being fed under the chip through the grooves. Concurrently, theportions of the cutting insert adjacent to the grooves will be cooledconsiderably better than the corresponding surface portions of aconventional cutting insert without grooves for the cooling liquid. Inother words, the temperature of the chip as well as of the cutting edgeportion of the cutting insert can be radically reduced.

In comparison with the embodiments according to FIGS. 5 and 10, theembodiments according to FIGS. 1 and 4 have the advantage that thecooling liquid supplied can pass out through the ends of the grooves 8,which open, into the flank 4.

What is claimed is:
 1. A metal-cutting insert for chip removingmachining, comprising a top side, a bottom side, a side surfaceextending between the top side and the bottom side, and a metal-cuttingedge disposed between the top side and the side surface; the top sideincluding a plurality of upwardly open grooves, each groove extendingtransversely toward the cutting edge from a groove inner end to a grooveouter end, the groove outer end terminating at least closely adjacentthe cutting edge for conducting cooling fluid toward the cutting edge;projections projecting upwardly from the top surface and defining chipdeflectors arranged in alternating relationship with the grooves; atleast an outer portion of each projection being disposed closer to thecutting edge than is the inner end of an adjacent groove; the outer endsof the grooves intersecting the top side at a location disposed at alower elevation than an uppermost portion of each projection; whereinthe outer ends of adjacently disposed ones of the grooves are spacedapart by a land defined by the top face, a width of the land beinggreater than a width of the outer end of each of the grooves.
 2. Themetal-cutting insert according to claim 1 wherein each groove has sidewalls which diverge in an upward direction as seen in a cross section ofthe groove lying in a plane oriented parallel to the cutting edge. 3.The metal-cutting insert according to claim 2 wherein each groove has adepth greater than a width of the outer end of the groove.
 4. Themetal-cutting insert according to claim 3 wherein the outer end of eachgroove is spaced inwardly from the cutting edge.
 5. The metal-cuttinginsert according to claim 3 wherein the outer end of each grooveintersects the cutting edge.
 6. The metal-cutting insert according toclaim 1 wherein the outer end of each groove is spaced inwardly from thecutting edge.
 7. The metal-cutting insert according to claim 1 whereinthe width of the land is greater than two times the width of the outerend of each of the grooves.
 8. The metal-cutting insert according toclaim 7 wherein the outer portion of each projection is disposed fartherfrom the cutting edge than are the outer ends of adjacent grooves. 9.The metal cutting insert according to claim 1 wherein the insert is ofpolygonal shape as viewed in top plan.
 10. The metal-cutting insertaccording to claim 9 wherein the outer end of each groove is spaced fromthe cutting edge.
 11. The metal-cutting insert according to claim 9wherein the outer end of each groove intersects the cutting edge. 12.The metal-cutting insert according to claim 1 wherein the insertincludes a cutting edge disposed between the top side and each of aplurality of the side surfaces, each cutting edge provided with thegrooves and projections.
 13. The metal-cutting insert according to claim1 wherein the cutting insert includes a cutting corner, a grooveextending toward the cutting corner, and projections disposed onopposite sides of that groove.
 14. A method of supplying cooling fluidto a metal-cutting edge of a metal-cutting insert during chip removingmachining of a metallic workpiece, the cutting insert being of polygonalshape as viewed in top plan and comprising a top side, a bottom side, anumber of side surfaces extending between the top side and the bottomside, and a cutting edge disposed between the top side and at least oneof the side surfaces; the top side including a plurality of upwardlyopen grooves, each groove extending transversely toward the cutting edgefrom a groove inner end to a groove outer end, the groove outer endterminating at least closely adjacent the cutting edge for conductingcooling fluid toward the cutting edge; projections projecting upwardlyfrom the top surface and defining chip deflectors arranged inalternating relationship with the grooves; at least a portion of eachprojection disposed closer to the cutting edge than is the inner end ofan adjacent groove; the method comprising directing a jet of coolingfluid toward the grooves from a location spaced inwardly from the innerends of the grooves, whereby the cooling fluid travels between theprojections and within the respective grooves toward the cutting edge.